# Write `len` bytes from `native`.
	private fun write_native(native: CString, from, len: Int)
	do
		if last_error != null then return
		if not _is_writable then
			last_error = new IOError("Cannot write to non-writable stream")
			return
		end
		if _file.as(not null).address_is_null then
			last_error = new IOError("Writing on a null stream")
			_is_writable = false
			return
		end
		var err = _file.as(not null).io_write(native, from, len)
		if err != len then
			# Big problem
			last_error = new IOError("Problem in writing : {err} {len} \n")
		end
	end